Multilayered polyester film

Abstract

A multilayered polyester film which comprises a polyester film and, disposed on at least one surface thereof, a layer X which has a contact angel HX(1) with water of 0-60°, wherein the layer X has a degree of crystallinity C(0) of 0-30%. HX(1): Contact angle at one second after water has come into contact with layer X. A polyester film having excellent recoverability is provided by disposing a layer X on at least one surface of a polyester film, the layer X having a regulated contact angle with water and a regulated degree of crystallinity.

The invention claimed is: 
     
       1. A multilayered polyester film which comprises a polyester film and a layer X which is disposed on at least one surface of the polyester film, wherein
 the polyester film comprises a polyethylene terephthalate or polyethylene-2,6-naphthalenedicarboxylate film, 
 
       the layer X
 consists essentially of a polyvinyl alcohol based resin that has a saponification degree of 30 or more and 88 or less, has a polyvinyl alcohol structure as a main chain structure and optionally contains 3 to 20 mol % of a member selected from the group comprising a 1,2-ethanediol group, a carboxyl group and a sodium sulfate group, 
 has a water contact angle HX(1) of 0° or higher and 60° or lower, 
 has a degree of crystallinity C(0) of 0% or more and 30% or less, and 
 has an absolute value of the difference between HX(20) and HX(1)(|HX(20)−HX(1)|) of 5° or higher, 
 wherein
 HX(1) is the contact angle at one second after water has come into contact with layer X and 
 HX(20) is the contact angle at twenty seconds after water has come into contact with layer X, and 
 
 
       the layer X is removable from the polyester film by washing with only water. 
     
     
       2. The multilayered polyester film according to  claim 1 , wherein the degree of crystallinity C(150) of the layer X after a heat treatment at 150° C. for 30 minutes is 0% or more and 30% or less. 
     
     
       3. The multilayered polyester film according to  claim 1 , wherein a ratio Ra/Xt of a surface roughness Ra (nm) of the polyester film on a side where the layer X is provided to a thickness Xt (nm) of the layer X is 0.001 or more and 1.0 or less. 
     
     
       4. The multilayered polyester film according to  claim 1 , further comprising:
 a layer Y that consists essentially of a silicone resin having a dimethylsiloxane structure as a main chain structure, has a water contact angle HY(1) of 80° or higher and 120° or lower, and is disposed on a surface of the layer X which is opposite to the layer X surface in contact with the polyester film, 
 wherein the water contact angles HY(1)(°) and HY(20)(°) of the layer Y of the film satisfy the following formula:
   45≤| HY (1)− HY (20)|≤80
 
 
 wherein
 HY(1) is the contact angle at one second after water has come into contact with layer Y and 
 HY(20) is the contact angle at 20 seconds after water has come into contact with layer Y, and 
 
 
       wherein the layer Y is removable from the polyester film by washing with only water. 
     
     
       5. The multilayered polyester film according to  claim 4 , wherein a layer Z is provided on a surface of the layer Y which is opposite to the layer Y surface in contact with the layer X, the layer Z comprises a ceramic green sheet containing barium titanate as a main component, and the layer Z is removable from the multilayered polyester film. 
     
     
       6. A multilayered polyester film including a polyester film and a layer Y, wherein
 the polyester film comprises a polyethylene terephthalate or polyethylene-2,6-naphthalenedicarboxylate film, 
 the layer Y consists essentially of a silicone resin having a dimethylsiloxane structure as a main chain structure, 
 water contact angles HY(1)(°) and HY(20)(°) in the layer Y satisfy the following formulas:
   80≤ HY (1)≤120 and
 
   10≤| HY (1)− HY (20)|≤80
 
 
 wherein
 HY(1) is the contact angle at one second after water has come into contact with layer Y and 
 HY(20) is the contact angle at 20 seconds after water has come into contact with layer Y, and 
 
 
       the layer Y is removable from the polyester film by washing with only water.